1. Field of the Invention
The present invention relates to a vehicle-direction detecting apparatus using a geomagnetic sensor and an angular velocity sensor.
2. Description of Background Information
In an on-vehicle navigation system, running direction of the vehicle is detected by a direction detecting apparatus for later display of that direction. In order to detect the direction, the direction detecting apparatus uses a geomagnetic sensor for detecting the intensity of geomagnetism in the X and Y directions perpendicular to each other on the same plane where the vehicle lies, as well as an angular velocity sensor for detecting the angular velocity of the vehicle. The direction detecting apparatus using those sensors has, however, been unable to detect the direction of the vehicle correctly, resulting in abnormal detection, because the geomagnetic sensor is affected by the magnetization of the steel plate of the vehicle body or the declination or the angle difference between the north on a map (true north) and the north indicated by the geomagnetism (compass north), and because the angular velocity sensor cannot detect other than the relative direction and its performance varies with the time. Therefore, there is a demand that the direction detected by the sensors in such an abnormal state be compensated to provide the correct direction.